A method is needed to make the most direct electrical connection from an interconnect's contact tip to the substrate upon which the interconnect is mounted. Currently, electrical continuity from an interconnect contact tip to the mounting substrate is by use of thin film aluminized traces that are wire bonded to the substrate. However, inductance, capacitance, and resistance increase with trace length and can degrade the electrical performance of the interconnect. Additionally, wire bond loop height must be kept at very low profile above the interconnect chip to prevent the wire bonds from touching the device under test.
A more direct and robust electrical contact from the interconnect contact tip to the mounting substrate would be to form a via in the vicinity of the interconnect contact tip through the full thickness of the wafer to the underside of the wafer. However, due to the thickness of the wafer, and/or the high aspect ratio of the via, conventional plating of the sides of such a “through-via” with metal is not practical, requiring other means of filling the via. A hallmark of this invention is to provide a process for filling a through-via that is formed through the thickness of a wafer with a conductive material.